Multi-phase fluid flow may have at least two phases: a fluid phase (e.g. oil phase) and a vapor phase (e.g. gas). In some cases, a multi-phase fluid flow may have three phases: a heavy fluid phase (e.g. aqueous phase), a light fluid phase (e.g. oil phase) and a vapor phase. Multi-phase fluid flow in a conduit can be encountered in industries, such as petrochemical plants, oil/gas production fields, and food stuff processing plants. It may be useful to measure and interpret characteristics of multi-phase fluid flow.
Multi-phase fluid flows may be encountered in the oil/gas production industry. In an oil/gas production context, various flow regimes reflective of various multi-phase fluid flows may be found, such as stratified flow, wavy stratified flow, plug flow, slug flow, dispersed bubble flow, and annular flow. Annular flow refers to gas flowing at high velocities in a center of a borehole with a fluid confined to a thin film on walls of the borehole. Stratified flow can occur in horizontal wells when two or more phases are separated due to gravity. Wavy flow can result in stratified systems when interference occurs between the two phases traveling at different velocities.
Factors influencing the flow regimes can include a degree of borehole deviation and proportion of each phase; relative differences in phase densities, surface tension and viscosity of each phase; and average velocity. In a fluid-gas system, when small bubbles of gas are uniformly distributed, the flow regime can be referred to as dispersed bubble flow. When some of these bubbles aggregate to form larger bubbles, plug flow and slug flow can result.
Understanding the multi-phase fluid flow regime in a conduit or pipe may be used to understand how a production well is performing. A production log records one or more in-situ measurements that describe the nature and behavior of fluids in or around the borehole during a production operation, including an injection operation. Production logs can provide, for example, information about dynamic well performance, and the productivity or infectivity of different zones. This information may be used to help diagnose problem wells, or monitor the results of a stimulation or completion.
Various downhole tools can be used for making downhole measurements used to produce logs, including flowmeters (e.g., spinners), local probes, nuclear logging tools, phase-velocity logging tools, production logging sensors, etc. Downhole tools may be used to measure various downhole parameters, such as temperature, flow rate, density, phase velocity, phase holdup, mixture density, mixture velocity, water (or liquid) holdup, water velocity, gas holdup, and the like.